1. Field of the Invention
The present invention relates to a working machine to which a structure for assembling a division type boom is installed.
2. Description of the Related Art
An attachment of a working machine for demolishing buildings, collecting and loading rubble, crushing stones and the like is replaced by other attachment which has a different specification in accordance with a work object (such as demolition, rubble collection and loading), work height (such as a high place and a low place) and the like (refer to Japanese Utility Model Laid-Open No. Sho64-28452).
For example, when a demolition work or the like is performed on a low rise structure, a first attachment A1 having a fundamental separate specification which is a basic specification shown in FIG. 11A is used. When the demolition work or the like is performed on a middle rise structure, a second attachment A2 having an extension separate specification shown in FIG. 11B is used.
As a common configuration among both the first and second attachments A1 and A2, an arm 2 is attached to a front end of a boom 1, a working device (a crusher shown in the figure or a backhoe bucket) 3 is attached to a front end of the arm 2, and a base end part of the boom 1 is attached to a base machine B so as to be raised and lowered around a boom foot pin 4.
The reference numeral 5 denotes a first boom cylinder (a raising and lowering cylinder) provided between the base machine B and the boom 1 for raising and lowering the entire attachment. The reference numeral 6 denotes an arm cylinder provided between the boom 1 and the arm 2 for rotating the arm 2. The reference numeral 7 denotes a working device cylinder provided between the arm 2 and the working device 3 for rotating the working device 3.
In the case of the first attachment A1 in FIG. 11A, the boom 1 is formed by a main boom body 8 on the base end side, and a front boom body 10 coupled to a front end of the main boom body 8 to rotate around a horizontal pin (hereinafter, referred to as a rotation spindle) 9. The front boom body 10 is rotated and folded into a reverse V shape by a second boom cylinder 11 provided between both the boom bodies 8 and 10.
In the second attachment A2 in FIG. 11B, one or more extension boom body 12 (a description will be given to a case of a single extension boom body shown in the figure) is fixed and connected to the main boom body 8 of the first attachment A1 with horizontal pins 13 and 14 on the upper and lower sides in a state that the boom is horizontal. The extension boom body 12 and the front boom body 10 are coupled to each other by the rotation spindle 9, and the second boom cylinder 11 is attached between the extension boom body 12 and the front boom body 10.
A structure of connecting the main boom body 8 and the extension boom body 12 at the time of assembling the second attachment A2 in FIG. 11B or at the time of replacing the first attachment A1 by the second attachment A2 in such a working machine is already shown in Japanese Utility Model No. 2535667.
A description will be given to the above conventional technique with FIGS. 12 to 15.
Upper pin holes 15 and 16 are provided in an upper part of a front end of the main boom body 8 and an upper part of a base end of the extension boom body 12 (the upper parts are on the upper side in a state that the boom is horizontal, the direction hereinafter is all the same), and lower pin holes 17 and 18 are provided in lower parts thereof.
A hook 19 opening upward is provided nearer to the front end than the upper pin hole 15 in a front end part of the main boom body 8. Meanwhile, a boss (normally, a round pin) 20 horizontally extending in the boom width direction is provided on an outer surface nearer to the front end than the upper pin hole 16 in a base end part of the extension boom body 12.
It should be noted that both the boom bodies 8 and 12 are formed into a box shape and symmetrically connected by pins on both the left and right sides of ends thereof. Therefore, the pin holes 15 to 18, the hook 19 and the boss 20 are provided on both the left and right sides respectively. However, in the description of the above conventional technique and a description of embodiments mentioned later, the left and right will not be distinguished for simplification.
Connection processes for both the boom bodies 8 and 12 are as follows.
(i) As shown in FIG. 12, the main boom body 8 is attached to the base machine B, while the extension boom body 12 is supported on mounts 21 in a state that the boss 20 is horizontal. The figure shows a case where the extension boom body 12 is supported on the mounts 21 in a state that other attachment elements including the extension boom body 12 (a second boom body cylinder, an arm cylinder and a working device cylinder are omitted) are already assembled.
(ii) The base machine B is moved and the hook 19 is engaged with the boss 20 from the lower side as shown in FIG. 13. In the above stage, the upper and lower pin holes 15 to 18 are not matched with each other.
(iii) The first boom cylinder 5 is elongated in the above state and the main boom body 8 is rotated upward (a scooping action).
By the above scooping action, the extension boom body 12 is rotated in the gradually lowering direction (downward rotation) around the boss 20. Therefore, the upper pin holes 15 and 16 and the lower pin holes 17 and 18 are matched with each other.
(iv) As shown in FIG. 14, the upper pin 13 is inserted into the matched upper pin holes 15 and 16, and the lower pin 14 is inserted into the lower pin holes 17 and 18 so as to connect both the boom bodies 8 and 12 to each other.
However, according to the above conventional technique, there is a need for bringing the hook 19 and the boss 20 into contact with each other as shown in FIG. 14 in a state that the upper pin holes 15 and 16 and the lower pin holes 17 and 18 are matched with each other (a connection state). Therefore, at the stage after removing the mounts 21 or at the time of work after assembling, an attachment load is imposed not only on both the pins 13 and 14 but also on an engagement part between the hook 19 and the boss 20. As a result, there is a problem that the hook and the boss are broken.
In order to prevent the problem, as shown in FIG. 15, positional relationships between the hook 19 and the boss 20 and the pin holes 15 and 16 and the pin holes 17 and 18 have to be set so as to generate a clearance C in the engagement part between the hook 19 and the boss 20 in a state that the upper pin holes 15 and 16 and the lower pin holes 17 and 18 are matched with each other.
However, when the positional relationships are set as above, the pin holes 15 and 16 and the pin holes 17 and 18 are taken away from an arc around a center of the boss at the time of the scooping action in FIG. 13. Therefore, the pin holes 15 and 16 and the pin holes 17 and 18 are not matched with each other only by the scooping action. Thus, pin hole matching becomes troublesome and hence it is not possible to sufficiently achieve an initial object of simplifying the pin hole matching with the hook 19 and the boss 20.
It should be noted that as another method, the upper pin holes may be matched by first relative rotation around the boss 20, and the lower pin holes may be matched by second relative rotation around the upper pin 13 (the pin holes are matched in order from the upper side and with a different center, the above method will be referred to as a two-step pin hole matching method hereinafter). However, according to the conventional technique, the hook 19 is moved upward and the boss 20 is moved downward at the time of the second relative rotation so that the hook 19 and the boss 20 are abutted with each other. Therefore, it is not possible to perform rotation itself.